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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 21 (1995), S. 571-590 
    ISSN: 0271-2091
    Keywords: CDF ; predictions ; laser Doppler anemometry ; inlet port ; cylinder ; turbulence ; steady flow ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: This paper presents a combined experimental and computational study of the steady flow through an internal combustion engine inlet port. The port was of generic design with a straight centreline. The three-dimensional velocity and turbulence fields in the port and cylinder were simulated using a computational fluid dynamics programme. Laser sheet flow visualization and laser Doppler anemometry were also employed to investigate the flows and assess the predictions. The results show that a large-scale flow structure is created in the cylinder by the inlet jet and its interaction with the valve and cylinder walls. Both predictions and measurements show that the flow is strongly dependent on the valve lift but is not affected by the flow rate. Comparisons of the numerical predictions with the experimental data indicated that the mean flow features are accurately predicted in many parts of the flow field; some discrepancies are evident and stem primarily from the failure of the simulation to predict a small recirculation region in the port which affects the trajectory of the annular jet entering the cylinder. Calculations were also made without modelling the port shape by using simplified inlet conditions upstream of the valve seat. It was found that this approximation can provide a reasonable, albeit less accurate, description of the flow, but modelling of the port shape is necessary for accurate flow predictions.
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 14 (1992), S. 1437-1452 
    ISSN: 0271-2091
    Keywords: Vortex flow aerodynamics ; High angle of attack ; Delta wing ; Viscous vortex models ; Vortex separation and bursting ; Computational fluid dynamics ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A new computational approach is developed for the analysis of vortex-dominated flow fields around highly swept wings at high angles of attack. In this approach an inviscid Euler technology is coupled with viscous models, similar to inviscid/boundary layer coupling. The viscous nature of the vortex core is represented by an algebraic model derived from the Navier-Stokes equations. The approach also accounts for the effects of the viscous shear layer near a wing surface through a modified surface boundary condition. The inviscid/viscous coupling consistently provides improved predictions of leading edge separation, vortex bursting and secondary vortex formation at relatively low computational cost. Results for several cases are compared with wind tunnel tests and other Euler and Navier-Stokes solutions.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 22 (1996), S. 1023-1035 
    ISSN: 0271-2091
    Keywords: convergence acceleration ; preconditioning ; multigrid ; GMRES ; ADI ; ILU ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Several solution acceleration techniques, used to obtain steady state CFD solutions as quickly as possible, are applied to an implicit, upwind Euler solver to evaluate their effectiveness. The implicit system is solved using either ADI or ILU and the solution acceleration techniques evaluated are quasi-Newton iteration, Jacobian freezing, multigrid and GMRES. ILU is a better preconditioner than ADI because it can use larger time steps. Adding GMRES does not always improve the convergence. However, GMRES preconditioned with ILU and multigrid can take advantage of Jacobian freezing to produce an efficient scheme that is relatively independent of grid size and grid quality.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 8 (1974), S. 341-358 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A least square based finite element algorithm is developed for some elasto-static problems. In the formulation both stresses and displacements appear as simultaneous variables. In two dimensional (plane) analysis, parabolie isoparametric elements are used. Considerable improvement of performance is obtained with a numerical integration based on 2 × 2 Gauss point distribution over more accurate integration schemes. Reasons for this are presented.The formulation is extended in the section ‘General least square formulation’ to beams and plates with a similar success of ‘reduced’ integration.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 2019-06-28
    Description: Models for scattering from a vegetation layer treated as a collection of discrete scatterers usually assume far field interaction among scatterers. In a real vegetation medium such as a deciduous forest it is not always true that each leaf is in the far field of the others. This paper examines the additional effect when scatterers are permitted to be in the Fresnel zone. It is found that this in general causes the backscattering coefficient to be higher and also to have a larger rate of increase with frequency than the case of purely far field interaction.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Format: text
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  • 6
    Publication Date: 2019-06-27
    Description: There are no author-identified significant results in this report.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E76-10199 , NASA-CR-146290 , REPT-75-6
    Format: application/pdf
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  • 7
    Publication Date: 2019-06-27
    Description: There are no author-identified significant results in this report.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E76-10179 , NASA-CR-146378 , REPT-75-4
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  • 8
    Publication Date: 2019-06-27
    Description: The author has identified the following significant results. Skylab photographs are superior to ERTS images for photogeologic interpretation, primarily because of improved resolution. Lithologic contacts can be detected consistently better on Skylab S190A photos than on ERTS images. Color photos are best; red and green band photos are somewhat better than color-infrared photos; infrared band photos are worst. All major geologic structures can be recognized on Skylab imagery. Large folds, even those with very gentle flexures, can be mapped accurately and with confidence. Bedding attitudes of only a few degrees are recognized; vertical exaggeration factor is about 2.5X. Mineral deposits in central Colorado may be indicated on Skylab photos by lineaments and color anomalies, but positive identification of these features is not possible. S190A stereo color photography is adequate for defining drainage divides that in turn define the boundaries and distribution of ground water recharge and discharge areas within a basin.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E76-10383 , NASA-CR-144513 , REPT-75-7
    Format: application/pdf
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  • 9
    Publication Date: 2019-06-27
    Description: The author has identified the following significant results. Skylab S190A photography used in a stereo mode is sufficient for defining the drainage divides and drainage patterns at the regional level. This data, combined with geologic information, define the boundaries and distribution of ground water recharge and discharge areas within the basin.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: E76-10198 , NASA-CR-146289 , REPT-75-5
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  • 10
    Publication Date: 2019-06-27
    Description: Three major investigations using LANDSAT and Skylab imagery concerned with analyses of color anomalies and linear features of central Colorado are discussed. The studies conducted are concerned with the geological significance of spectral and spatial features on the images. Color anomalies in Skylab photographs were analyzed and evaluated for locating indicators of mineralization. The relationships were determined of all linear features in a LANDSAT image to the rock joint systems and the detectable larger geologic structures; techniques for extracting that geologic information are indicated. Some anomalous megalinear features in LANDSAT and Skylab images are analyzed which transect major structures and, their associated geologic features are described.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: G-10 , NASA. Lyndon B. Johnson Space Center NASA Earth Resources Surv. Symp., Vol. 1-B; p 713-760
    Format: text
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